In addition to the Color track, the Spotlight and Point Light tracks contain a Parameter Track in which the Range, Angle and Falloff key data is stored. Please read the Intensity, Beam and Falloff and Range of Point Light sections for more information.
Since there is no On/Off key for lights we will use the Range parameter to simulate a Turn On effect for a Spotlight or Point Light.
Go to the desired frame and set the Range value to 0.
Go to the next frame and increase the Range value.
The light is turned on by setting two keys in the Parameter track.
